1. Field of the Invention
The present invention relates to an upper audio range (UAR) hearing apparatus and method that converts speech waveform envelope into upper audio frequencies ( greater than 10 kHz), for delivery to the ear, or skin of the head or neck, which are then provided to the inner ear and then the brain.
2. Description of the Related Art
Conventional air conduction hearing aids only amplify either the entire speech signal or certain portions, or frequency bands, or the speech signal. The most intense part of speech is the fundamental frequency derived from action of the vocal folds. Higher frequencies are derived from vocal tract resonance, but their intensities are lower than those of the fundamental frequency.
The relatively lower intensity, higher frequency speech sounds are generally consonants. Consonants carry most of the information in speech, and are important for normal speech perception. In the cases of sensorineural hearing loss, consonant detection is altered, as is intelligibility. As mentioned above, conventional aid conduction hearing aids focus on amplifying all or portions of the speech spectrum to regain intelligibility for persons with hearing loss. Conventional air conduction hearing aids are ineffective at some degree of hearing loss, depending on the nature of the loss and the individual differences. Alternative approaches have included using frequency bands not compromised by the hearing loss. One approach, disclosed in U.S. Pat. No. 4,982,434, involves frequency-converting the speech to an ultrasonic region ( greater than 30,000 Hz), while another approach involves frequency transposition focusing the speech into a bass region ( less than 300 Hz). The upper audio range, from about 10,000 Hz to 29,999 Hz, has been neglected.
The invention is directed to a hearing aid, which includes a plurality of channels for receiving an input speech signal, one of the channels filtering the speech signal with a first filter centered at a first predetermined audio frequency and having a first predetermined filter bandwidth, another of the channels filtering the speech signal with a second filter centered at a second predetermined audio frequency and having a second filter bandwidth. The hearing aid also includes an envelope extraction unit for extracting an envelope of an output of each of the channels, and a multi-channel frequency multiplication unit for performing a modulation of each of the envelopes obtained from the output of each of the channels using a carrier that is in an upper audio frequency range. The hearing aid further includes a transducer unit for providing vibration and sound in the ear canal or preferably as a vibration to the skin of a user based on the modulated envelopes.